QCD phase diagram and its application in compact stars A holographic hardwall approach

Abstract

Matter making up the interior of stars consists of an interacting soup of nucleons and newlinephotons. Calculating the equations of state of this nuclear matter at high densities and newlinetemperatures is complicated by the strong nature of the interactions among the nucleons newlineand the multiple energy scales involved. A radical new approach to these systems called newlineAdS holography tries to obtain the equations of state via gravity calculations in higher newlinespacetime dimensions. In this thesis, we have obtained the equations of state and a phase newlinediagram of QCD-like theories at large densities and low temperatures by using a particular newlineversion of holography termed the hardwall model. newlineWe have generalized the hardwall model to 10-d with D7-branes which allowed us newlineto compute the phases at finite temperatures for various quark masses. This approach newlineproduces phenomenologically interesting inequalities, also at nonzero density. However, newlinewe had to return to the 5D hardwall models to study the nature of a suitable hologram newlineof the low density confined phase. An important contribution of our work is the use of newlinemodified IR boundary conditions which incorporate phenomenology. Furthermore, we newlineanalyzed baryonic condensates within these confined phases. Interestingly, we find that newlinecondensing operators have a restricted range of scaling dimensions. newlineThe equations of state derived in these phases are then utilized to calculate the mass- newlineradius relation of compact stars. We conclude that the cores of compact stars will exhibit newlinecondensates at low temperatures and supranuclear densities. newline